Jakarta is subsiding rapidly. North Jakarta has dropped several metres in the past 35 years. Many areas are already several metres below sea level and that poses a serious threat to the population and infrastructure. If nothing is done, North Jakarta will be hit by prolonged flooding more frequently. The damage runs into millions of dollars each year and more than four million people are at risk.
At the moment, most efforts are focusing on adaptation measures: reducing the risk of flooding by building large flood defences and strengthening the existing sea wall as part of the National Capital Integrated Coastal Development (NCICD). However, the coastal defences will not solve the underlying problem: land subsidence. Researchers are engaged in a debate about the causes of the subsidence that is complicated by a lack of sound data.
To arrive at a consensus about the causes of land subsidence and to devise a concrete strategy to tackle the problem in Jakarta, Deltares organised a round-table discussion in collaboration with the Indonesian government. International subsidence experts sat at the table with policymakers and researchers from Indonesia. Experts from the US, Italy, Japan and the Netherlands shared their experiences about locations like Tokyo, Venice and Bangkok. Reducing or even stopping groundwater abstraction in these cities proved to be the key to preventing further subsidence.
The promising outcome was a new strategy that was presented to the Governor of Jakarta and the Minister of Public Works. The governor and the minister supported the new strategy of putting an end to the abstraction of deep groundwater and working on a 'zero policy’. They were eager to take on board the recommendation that government should lead the way and legislate against the use of groundwater in all government and public buildings. The intensification and improvement of monitoring are also important priorities in the strategy: it is important to know whether the measures are effective. In addition, the researchers and policymakers advised the establishment in 2016 of a subsidence task force for the city of Jakarta that will focus on measures to reduce subsidence.
Every country in the world is looking for a successful strategy for land subsidence. By setting out this strategy and through the efficient exchange of experience, cities can avoid reinventing the wheel and save a lot of time and
Deltares taught me how to use the software for groundwater modelling, IMOD. This really helped me to conduct a groundwater behaviour study in Jakarta in order to support the coastal development program in that location.
In this project Deltares worked together with the following partners: